The muscles on the back of my hand and the inside pad of my palm have shrunk. My grip is weak, and my hand seems clumsy. My doctor says it's from thoracic outlet syndrome. I've started doing exercises. Will the muscles heal, and will my strength come back?

Hand muscles that actually shrink suggest that you have had significant pressure on the ulnar nerve, which runs down your arm and into your hand. Once the pressure is removed, your hand strength should eventually come back. You may find that your strength returns before the muscles get bigger. Getting the muscles back to their original size may take some time.